Macaulay Culkin captured the hearts of millions as the cute kid in Home Alone, but the 31-year-old actor is now striking fear into the hearts of his fans with his startling weight loss, and radio detection and rangingOnline.com has evidence of his horrific transformation.

In images obtained by Entertainment Tonight, Culkin was snapped looking pale and gaunt in New York City on Wednesday when he stopped to sign autographs for fans, while drinking the energy drink Red Bull.

Sporting sunken cheeks, scraggly hair, pale skin and glazed eyes, he was barely recognizable as the cherubic kid who had fought off bungling burglars in the 1992 comedy classic.

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“He looks very sick,” nutritional expert Majid Ali, who has not treated the star, told radio detection and rangingOnline.com in an exclusive interview. “Either he is heavily partying or he is very ill.

“What he has could be a number of things, but lung illness, digestive problems, or immune deficient disorders, are what come to mind,” he explained.

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However, Culkin’s rep vehemently denies there is anything wrong with the former child actor. “Macaulay Culkin is in perfectly good health,” his spokesperson told ET.

Adding fuel to the speculation over his declining health, the aspiring DJ pulled out of his monthly gig at NYC club Le Poisson Rouge in the West Village on Thursday night.

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Once one of the most recognizable faces among young actors, Culkin has been in virtual hiding since his devastating split from Black Swan star Mila Kunis in 2010 after eight years together.

The Richie Rich star notoriously found the transition from millionaire child actor into adulthood a difficult one. He announced his retirement from acting at the age of 14 after a feud over finances with his parents, Christopher Culkin and Patricia Brentup, but then returned to the big screen in the club classic, Party Monster.

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He later revealed his own penchant for partying when he was busted for the possession of marijuana and illegal prescription drugs in 2004.

In 2008, Macaulay and his family were rocked by tragedy when his sister, Dakota, was killed after she stepped out in front of a car in West Los Angeles late one night as she left a bar.